> ## Documentation Index > Fetch the complete documentation index at: https://gomodel.enterpilot.io/docs/llms.txt > Use this file to discover all available pages before exploring further. # Create a message (Anthropic Messages API) > GoModel API reference for POST /v1/messages: Create a message (Anthropic Messages API). ## OpenAPI ````yaml /openapi.json post /v1/messages openapi: 3.0.0 info: description: >- AI gateway routing requests to multiple LLM providers (OpenAI, Anthropic, Gemini, Groq, Fireworks AI, Meta, OpenRouter, Kilo AI, DeepSeek, Z.ai, xAI, MiniMax, Xiaomi MiMo, OpenCode Go, Oracle, Ollama, Bailian). Drop-in OpenAI-compatible API. title: GoModel API contact: {} version: '1.0' servers: - url: '{base_url}' description: Edit the base URL to point at your GoModel deployment. variables: base_url: default: http://localhost:8080 description: Your GoModel deployment URL security: [] paths: /v1/messages: post: tags: - messages summary: Create a message (Anthropic Messages API) requestBody: $ref: '#/components/requestBodies/anthropicapi.MessagesRequest' responses: '200': description: JSON response or SSE stream when stream=true content: application/json: schema: $ref: '#/components/schemas/anthropicapi.MessagesResponse' text/event-stream: schema: $ref: '#/components/schemas/anthropicapi.SSEEventFrame' '400': description: Bad Request content: application/json: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' text/event-stream: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' text/event-stream: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' '429': description: Too Many Requests content: application/json: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' text/event-stream: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' '502': description: Bad Gateway content: application/json: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' text/event-stream: schema: $ref: '#/components/schemas/anthropicapi.ErrorResponse' security: - BearerAuth: [] components: requestBodies: anthropicapi.MessagesRequest: content: application/json: schema: $ref: '#/components/schemas/anthropicapi.MessagesRequest' description: Anthropic Messages request required: true schemas: anthropicapi.MessagesResponse: type: object properties: content: type: array items: $ref: '#/components/schemas/anthropicapi.ResponseContentBlock' id: type: string model: type: string role: type: string stop_reason: type: string stop_sequence: type: string type: type: string usage: $ref: '#/components/schemas/anthropicapi.Usage' anthropicapi.SSEEventFrame: description: >- One server-sent event frame emitted by streaming /v1/messages. On the wire each frame is sent as event: and data: . Unknown event payloads are accepted for forward compatibility. anyOf: - $ref: '#/components/schemas/anthropicapi.SSEMessageStartEvent' - $ref: '#/components/schemas/anthropicapi.SSEContentBlockStartEvent' - $ref: '#/components/schemas/anthropicapi.SSEContentBlockDeltaEvent' - $ref: '#/components/schemas/anthropicapi.SSEContentBlockStopEvent' - $ref: '#/components/schemas/anthropicapi.SSEMessageDeltaEvent' - $ref: '#/components/schemas/anthropicapi.SSEMessageStopEvent' - $ref: '#/components/schemas/anthropicapi.SSEPingEvent' - $ref: '#/components/schemas/anthropicapi.SSEErrorEvent' - $ref: '#/components/schemas/anthropicapi.SSEUnknownEvent' anthropicapi.ErrorResponse: type: object properties: error: $ref: '#/components/schemas/anthropicapi.ErrorObject' type: type: string anthropicapi.MessagesRequest: type: object properties: cache_control: type: object max_tokens: type: integer messages: type: array items: $ref: '#/components/schemas/anthropicapi.Message' metadata: $ref: '#/components/schemas/anthropicapi.Metadata' model: type: string output_config: description: >- OutputConfig carries structured output (format) and the effort level. allOf: - $ref: '#/components/schemas/anthropicapi.OutputConfig' output_format: description: >- OutputFormat is the deprecated top-level form of output_config.format. type: object stop_sequences: type: array items: type: string stream: type: boolean system: oneOf: - type: string - type: array items: $ref: '#/components/schemas/anthropicapi.ContentBlock' temperature: type: number thinking: $ref: '#/components/schemas/anthropicapi.Thinking' tool_choice: $ref: '#/components/schemas/anthropicapi.ToolChoice' tools: type: array items: $ref: '#/components/schemas/anthropicapi.Tool' top_k: type: integer top_p: type: number anthropicapi.ResponseContentBlock: type: object properties: data: description: Data is the opaque payload of a redacted_thinking block. type: string extra_content: description: >- ExtraContent is provider replay state on a tool_use block; clients echo it back on the next turn (see core.ExtraContentField). type: object id: type: string input: type: object additionalProperties: true name: type: string signature: description: >- Signature authenticates a thinking block. Anthropic requires it back verbatim when the conversation continues, so clients must echo it. Every thinking block carries the member, as the Anthropic schema requires; reasoning from a provider that does not sign its output is rendered with an empty signature. Hence the pointer: only a thinking block has one. type: string text: type: string thinking: type: string type: type: string anthropicapi.Usage: type: object properties: cache_creation_input_tokens: type: integer cache_read_input_tokens: type: integer input_tokens: type: integer output_tokens: type: integer anthropicapi.SSEMessageStartEvent: type: object required: - message - type properties: type: type: string enum: - message_start message: $ref: '#/components/schemas/anthropicapi.MessagesResponse' anthropicapi.SSEContentBlockStartEvent: type: object required: - content_block - index - type properties: type: type: string enum: - content_block_start index: type: integer content_block: $ref: '#/components/schemas/anthropicapi.ResponseContentBlock' anthropicapi.SSEContentBlockDeltaEvent: type: object required: - delta - index - type properties: type: type: string enum: - content_block_delta index: type: integer delta: type: object additionalProperties: true anthropicapi.SSEContentBlockStopEvent: type: object required: - index - type properties: type: type: string enum: - content_block_stop index: type: integer anthropicapi.SSEMessageDeltaEvent: type: object required: - delta - type properties: type: type: string enum: - message_delta delta: type: object additionalProperties: true usage: $ref: '#/components/schemas/anthropicapi.Usage' anthropicapi.SSEMessageStopEvent: type: object required: - type properties: type: type: string enum: - message_stop anthropicapi.SSEPingEvent: type: object required: - type properties: type: type: string enum: - ping anthropicapi.SSEErrorEvent: type: object required: - error - type properties: type: type: string enum: - error error: $ref: '#/components/schemas/anthropicapi.ErrorObject' anthropicapi.SSEUnknownEvent: description: Fallback for future Anthropic streaming event payloads. type: object required: - type properties: type: type: string additionalProperties: true anthropicapi.ErrorObject: type: object properties: message: type: string provider: description: |- Provider names the upstream provider that produced the error. It is omitted for errors raised by the gateway itself. type: string type: type: string anthropicapi.Message: type: object properties: content: oneOf: - type: string - type: array items: $ref: '#/components/schemas/anthropicapi.ContentBlock' role: type: string anthropicapi.Metadata: type: object properties: user_id: type: string anthropicapi.OutputConfig: type: object properties: effort: type: string format: type: object anthropicapi.ContentBlock: type: object properties: content: oneOf: - type: string - type: array items: $ref: '#/components/schemas/anthropicapi.ContentBlock' extra_content: type: object additionalProperties: true id: type: string input: type: object additionalProperties: true is_error: type: boolean name: type: string source: oneOf: - type: string - type: object additionalProperties: true text: type: string thinking: type: string signature: type: string data: type: string tool_use_id: type: string type: type: string anthropicapi.Thinking: type: object properties: budget_tokens: type: integer type: type: string anthropicapi.ToolChoice: type: object properties: disable_parallel_tool_use: type: boolean name: type: string type: type: string anthropicapi.Tool: type: object properties: cache_control: type: object defer_loading: description: >- DeferLoading marks a tool whose schema the API loads only when tool search matches it. It is an ordinary custom tool that declares itself deferred, so the translated pipeline sends it like any other and drops the marker (see convertTools). type: boolean description: type: string input_schema: type: object additionalProperties: true name: type: string strict: type: boolean type: type: string securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: JWT ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.